The invention relates to a method of spreading a sheet on a frame-like member such as a core member of a chair seat.
Conventional methods of spreading a square wire mesh on the square frame of a chair are disclosed, for example, in Japanese Examined Utility Model Publication No.Sho54-23523 and Japanese Examined Utility Model Publication No.Sho61-12830.
The former discloses that by inserting a steel wire into each of two opposite sides of a wire mesh, and attaching coil springs having hooks at both ends, with one hook to the steel wire and the other hook to the wire mesh, the wire mesh is spread with a prescribed tension charged against it, by taking advantage of the energizing force of the coil springs.
The latter discloses that a wire mesh is spread by inserting an adapter plate into each of two opposite sides of the wire mesh and then screwing or rivet caulking the adapter plates onto the metal frame while keeping a prescribed tension charged against the wire mesh.
In Japanese Examined Utility Model Publication No.Hei2-9723, it is disclosed that a cushion material made of cloth, having flexibility, is spread and fixed by wrapping the cushion material around the frame and bonding or sewing it to the same.
One of the major problems of a chair formed in accordance with the aforementioned prior arts is that such a chair is not comfortable to sit on because the wire mesh or the like, which is stretched in only two opposite directions, flexes in a limited number of directions.
When the prior arts are applied to products other than a chair (for example, a filter for an air conditioner made by spreading a mesh-like material on a frame member), there are disadvantages, as in the increased time it takes to assemble the larger number of parts, such as hooks and screws, or as in the increased difficulty in making products with an even tension charged against, thus making products of uneven quality.
In relation to a chair, it is described in Japanese Examined Utility Model Publication No. Sho54-6644 and Japanese Examined Patent Publication No.Sho54-20900 that a core member, on which a cloth covering is spread, is fit into a frame-like cover formed out of resin. It is described in Japanese Examined Utility Model Publication No. Sho56-21039 that a core member, on which a cloth covering is spread, is covered with an edge cover formed by extrusion molding of resin. Purportedly, these processes are employed in order to prevent the cloth covering from coming off, as well as, to protect the core member.
However, it takes a lot of time and effort to fit the edge member to a chair. There is also a problem that the edge member is apt to be in an uneven finished state and thus, might come off easily.